In my co-pending U.S. patent application Ser. No. 223,557, the text of which is incorporated herein by reference I have described apparatus and method for wrapping a resilient strip material about a mandrel with the wrapped strip being held firmly against the mandrel at the ends thereof as by collar means which prevent unwrapping the wrap, inserting the mandrel into a bore to be lined and creating a lining at a selected place within the bore by unwrapping the strip material from the mandrel to create a lining consisting of spirally placed strip, e.g., metal strip interleaved with layers of a curable liquid resin which is held in place against the bore by resilience of the strip and bonded together by effecting curing of the resin. A downhole tool for effecting the lining, a machine for wrapping the tool and a process for creating the new lining were disclosed. An extensive testing program has led to a number of improvements in the apparatus and process which have led to an improved leak resistance upon pressure testing of the linings produced. The present application is directed to a description of the said improvements.